The Myth of the 2,000 Calorie Diet
At Calorify, one of the most important metrics we report to you is your daily caloric burn. Everything in your body uses energy - your immune system, heart and lungs, kidneys and liver, your brain, and of course exercise and other physical activity. Also known as total energy expenditure (TEE), this is the total amount of energy that is required to power the ~37 trillion cells in your body each day. Your TEE is a measure of how your body is functioning, a peek into the hidden engine that powers your life.
How much power does that engine take? Well it depends on who you are as an individual. At Calorify, we have seen people burn anywhere from just under 2,000 to around 7,000.
So if we’re all burning different amounts, why do all of our food labels report calories based on a 2,000 calorie diet? Accompanied by an asterisk, most labels read, “Percent Daily Values are based on a 2,000 calorie diet. Your daily values might be higher or lower depending on your calorie needs.”
But what does that even mean? Where does the 2,000 come from? Is 2,000 average? How do I know if my caloric needs are higher or lower than 2,000? Let’s break it down.
So where does the 2,000 calorie diet come from?
The 2,000 calorie a day diet came to mainstream food labels in the 1990s after the Nutrition Labeling and Education Act of 1990 was passed. It required nutrition labels on all packaged food. The labels were to include what nutrients were in the food and how much is present. It was decided that Daily Reference Values (DRVs) would be more helpful to the average person than actual masses (grams, milligrams, etc.), so they needed a standard diet to reference, thus the need for a standardized caloric intake was born.
So, from 1994-1996, the USDA did a survey called the Continuing Survey of Food Intake by Individuals. They picked random people from across the country, varying in geographic location and income status. They then had phone interviews with each household and had them record information about their diet for a total of three days. Based on this nationwide survey, the average caloric intake the USDA found was 2,000 calories.
Seems like an okay plan, right? Ask how much people are eating and base the DRVs on that right? In theory it’s not a bad idea, but we know that people chronically undercount the calories they’re actually consuming, oftentimes by hundreds - or even thousands! - of calories. In the literature, it’s clear that Americans (and everyone else) underreport their caloric intake anywhere from 18.5% (Orcholski et al. 2015) to around 35% (Subar et al. 2003)—in other words 500-1,000 calories on average. Factors such as age, sex, and BMI can affect underreporting dramatically. In the USDA survey report, this is acknowledged by expressing concern about data quality, but little-to-nothing was done in the following years (i.e. ~30 years after this report came out and 2,000 cals is still what labels report). So…
Problem 1: People undercount their calories making the recommendation lower than what people actually eat.
That might be okay though, right? Just bump up the average a little to count for the undercounting and then it should be representative of the population? Well, not exactly. Not only would the number you should add be hard to justify, it still wouldn’t be representative of everyone, which leads us to the other problem with how the USDA came up with this number…
Problem 2: They included everyone in their calculation.
This brings us to the second question, is 2,000 actually average? In order to make their 2,000 calorie recommendation, the USDA did indeed average the average intakes across ALL ages–from infants all the way up to 100+ years old (yep, you read that right–ALL ages). The problem here is that your metabolism changes throughout your life, so they ignored the metabolic diversity we see across our population.
Calorify’s Scientific Advisor, Herman Pontzer, led a project that showed this relationship between age and metabolism. Basically, there are four different stages of metabolism you go through throughout your life: neonates (birth to 1 year old), juveniles (1 to 20 years old), adulthood (20 to 60 years old), and older adults (>60 years old). As expected, your metabolism increases rapidly in the neonate stage, and continues to increase at a steadier pace as a juvenile–you’re growing and your needs are changing constantly. As an adult, you’re done growing and this is the longest period of your life (the majority of Americans fall into this age group). Your metabolism is stable. Then finally, as an older adult, your metabolism starts to decline.
What this means for the 2,000 calorie diet calculation is that the USDA lumped a lot of different people together to simplify varying caloric needs to a single number. The USDA included calories eaten data all the way from 838 cals for those under 1 year old, to 2,821 cals for males aged 20-29 and everything in between–a spread of 2,000 calories apart, all going into the same single recommendation. In sum, your caloric needs as a person in your early twenties are going to differ significantly from your first year of life, so it’s interesting they’ve been lumped into the same calculation.
What if the USDA had only included adults (20-60 years) in their calculation?
The average still would have been low, at about 2,200 calories. However, using the data from the gold standard doubly labeled water database for the same age group, the average burn is actually closer to 2,725 calories - 40% higher than the standard recommendation on food labels you see every day!
In the graph to the right, you can see the spread of caloric needs across the population compared to the 2,000 calorie recommendation (dashed line). The three distinct stages showcase the difference in energy needs throughout life. You can also really see that the 2,000 calorie diet might only be appropriate for a few juveniles and some older adults, but that it’s seldom appropriate for adults. Take note of the width of the adult stage (shown in red)–ranging from about 1,200 all the way up to 5,000, with an average of 2,725–relatively few fall at or below 2,000 calories. At Calorify, we have even measured adult athletes all the way up to 7,000 calories.
The USDA has since begun to update their caloric requirements based on age, sex, and physical activity level, but you have to dig through their most recent report to find it (Table A2-2 for those who are curious). And even so, their recommendations still look a little low (e.g. the updated data show that an active adult should aim for about 2,550).
So it’s clear that 2,000 isn’t a catch all number, and doesn’t apply to the majority of people. How do you know if 2,000 calories is actually representative of your burn?
We know there isn’t another way to know how many calories you truly burn (even within +/- 1,000 calories) without measuring it, so take a Calorify test–we’ll help you stop guessing and start measuring!
References
Pontzer et al., 2021, Daily Energy Expenditure through the Human Life Course, Science
U.S. Department of Agriculture, 2020, Dietary Guidelines for Americans 2020-2025
